1. Field of the Invention
This invention relates to polymeric oil additives and to lubricating oil compositions containing these additives. More particularly, the present invention relates to hydrogenated, block copolymers of butadiene and another conjugates diene and, if desired, a vinyl aromatic monomer and their addition to lubricating oil compositions containing pour depressants with minimal affect on the pour point of said compositions.
2. Description of the Prior Art
Various copolymers of butadiene with other olefins are known as oil additives. Thus, U.S. Pat. No. 3,419,365 teaches hydrogenated copolymers of butadiene and styrene as pour point depressants for distillate fuel oil. Similarly, U.S. Pat. No. 3,393,057 teaches copolymers of butadiene, C.sub.10 to C.sub.24 normal alpha-monoolefins and styrene or indene as pour point depressants for fuel and lubricating oils. U.S. Pat. No. 3,635,685 discloses pour point depressants comprising hydrogenated butadiene-styrene copolymers which contain a hydroxy, carboxy, or pyridyl terminal group.
U.S. Pat. No. 3,312,621 discloses copolymers of various conjugated diolefins, including butadiene and isoprene which are predominantly in the 1,4-addition configuration as viscosity index (V.I.) improvers for lubricating oils.
Other styrene-diene copolymers have been reported for possible use in lubricants, including U.S. Pat. No. 3,772,196 which shows lubricating oil compositions for internal combustion engines containing a combination of block copolymers comprising a first polymer block of an alkenyl arene, e.g. styrene, and a second essentially completely hydrogenated polymer block of isoprene and certain pour point depressants in a lubricant base stock; and, U.S. Pat. No. 3,795,615 which teaches that a hydrogenated copolymer of butadiene and isoprene may be incorporated into mineral oil containing a polymeric pour point depressant to improve the viscosity index of the lubricating oil blend.